The use of mechanical restraints on nursing home residents, particularly restraints which tie a person into a chair is now severely limited by stringent government regulations. In the absence of such mechanical restraints, one problem that arises in a nursing home setting is that forgetful, demented or confused patients may seek to leave the confines of a chair without notifying a caregiver who could provide the needed assistance. Many nursing homes resort to the use of alarms to alert the caregiver that a patient is getting up from or has already left the safety of the seated position. Typically these alarms rely on a sensing device, generally a pressure sensor, that is located on the seat of a chair. An alarm sounds in response to a decrease in pressure, thus alerting the caregiver to a potentially dangerous situation. An example of such a device is found in U.S. Pat. No. 5,990,799.
Other devices use a string to tether a patient to an alarm box, which may be mounted onto a chair. When the patient attempts to leave, the patient pulls on the string thereby activating an alarm. Examples of this type of device are shown in U.S. Pat. Nos. 5,066,943 and 5,494,046.
Seat sensors have certain drawbacks. The position of the sensor pad on the seat is critical, because the sensor must be located on the spot that receives the greatest amount of sitting pressure. Also, the use of bedclothes, wheelchair cushions and other paraphernalia normally used or associated with a wheelchair can interfere with the operation of the sensor. Moreover, the use of a pressure sensor on top of a cushion (generally the preferred location) interferes with the cushioning effect, which can have deleterious effects on the health of a patient, such as the increased probability of pressure sores. Finally, the sensor pad is subject to relatively large mechanical forces, which can bend and/or flex it leading to a diminished useful lifetime because of mechanical or electrical contact failure.
Another problem arising in a nursing home setting is the tendency for a patient to slide forward in a wheelchair (sacral sitting). Sliding forward in a wheelchair places unnecessary and sometimes dangerously high forces on the sacrum. In addition, the awkwardness of the sacral sitting position can severely interfere with functioning of the patient for such things as feeding, upper arm movements and breathing.